Dispersion of fluorochlorocarbon polymers



United States Patent 2,775,569 1 DISPERSION F FLUonoeHLoRocA-RiioN PULYMERS CharlesD. Dipner, Jersey-City,Wilber 0. Teeters,-River 5 Edge, and John M. Wrightsoir,'North Bergen, N,. J., assignors to The M. W. KelldggCompany, Jersey City, 'N. J.,-a corporation of Delaware No Drawing. Application December 30, 1949,

Serial No. 136,163 17 Claims. (Cl. 260-323) This invention relates to dispersions of high molecular Weight polymers of perfluorochlorocarbons as the monomers. Inone aspect this invention relates to dispersions of suspensions of the normally waxy and plastic polymers of the single monomer trifluorochloroethylene. in another aspectthe invention relates to a method forappl'ying plastic polymers of trifiuorochloroethylene to surfaces;

Polymers of trifluorochloroethylene possess cei-tain physical and chemical characteristics which make the poly mers particularly desirable as surface coatings and il'l'lpregnants. The plastic polymer produced'from the single monomer trifluorochloroethylene is hard but not brittle and is flowable under pressure at temperatures above 225 C. The polymers of triiluorochloroe thylene in general possess excellent mechanical properties, resistance to chemicals and oxidation, flame resistance, superior electrical properties and high working temperatures. ourfifth's of the Weight of the polymer of the singlenidhomer'. is made of the two halogens,-fluorineand chloride; The quick quenched plastic polymer is colorless and tran parent. The'polymer has a high chmicalstability, no effect being observed on the polymer after prolongedeir j po'sure to" concentrated sulfuric acid, hydrofluoric: acid, hydrochloric acid, strong'caustic,=fuming nitric aeid,aqu'af 35 regia, andother vigorous oxidizing materials: 5 The 'pla'sti polymer is flexible and resilient, has a high strength at low temperatures and is resistant to'th shock. The polymer is notwet'tedby water and 1 affectedby highhumidity. Table I below shows some of theelectrical characteristics of the" normally sdlid" polymer under high frequency:

Other physical properties ofthe plastic polymeraie' 1 shown below in Table II: TABLE II Property Test Result" Specific gravity; 2.1. Tensile strength at 86 F., p. s. 9,400.

Elongation at break 86F., percent... 7. Ooefiici eut ,of linear expansion (-320 F. to 3.5X10- 107 Specific resistance, ohms 5X10": Water absorption, percent 0.00. Outdoor weathering 2,775,569 Patented Dec. 25, 1956 Normally solid polymers produced from the single monomer 'trifiuorochloroethylene may be prepared by p61 erizing the monomer in the presence of a suitable peroxide such as bistrichloroacetyl peroxide, as the polymerizing agent, at a temperature between about ,20 and about 25, C., preferably at a temperature of about l6 C. At a temperature of l6 C. the polymerization of t'rifiuorochloroethylene to a satisfactory yield of solid polymer is accomplished in about seven days. "At elevated temperatures and at corresponding superatmospheric pressures less time is required to complete the polymerization. As this invention does not reside in thepreparati-on of the polymer per se, further dis cussion thereof is deemed unnecessary. y

To distinguish the plastic polymer over the oils and waxes produced with the same monomer, the polymer is described by reference to its no strength temperature. A no'strength temperature (N. S. T.) of between about 210 and about 350 C. is characteristic of a normally solid polymer of the above preparation having plastic characteristics. Best plastic characteristics of the normally solid polymer ar'e observed at N. S. T. valuesbetweenabout 240 and "about 340* C. The N. S. T.values of the polymer depend upon'such factors as temperature, residencetime, concentration of promoter, pressure, etc. Sincejhis invention does not relate to themefhod of producing the polymer of particularcharacteristics, further discussion ther'eofv'vill not be undertaken. Other applicationshave been filed relating to the preparation of the polymer per se. The'no strength temperature (N. S. T.)'is determined in the'following manner: A sample of polytriflnorochloroethylene is hot pressed into a V thick sheet and cut into a strip of As it 1 X 1%". The strip is notched A from the top so that the dimension at the notch shall, be x 6 A'fine wire and'a standard Weight is attached to one end of the strip. The weight of the polymer plus the wire and standard Weight shall equal A2 gram. The

strip is then attached in a furnace and fixed vertically therein. The temperature of the sample is increased at a rate ofabout 1%" C. per minute in the furnace as the breaking temperature is approached. The no strength temperature is the breaking temperature ofthe sample.

Difference's'of about 5 C. are considered significant.

As a result of the excellent chemical and physical properties of the polymers of tiifluorochloroethylene, the

', polymers have use as coatings on various surfaces in ordertd make such surfaces corrosion resistant to chemicals. The good electrical, non-wetting and flame resis'tantproperties of the polymer also makes its use feasible as insulatin'gijcoatings on electrical conductors,

. condensers and various parts used in electrical apparatus and circuits. The polymer may be applied to various surfaces, including flat and curved surfaces, Wires, fabrics, yarn, paper, leather, cables, cans, glass, wood, etc. The polymer may be applied to metal wires, particularly aluminum, iron and copper, to act as an insulator on the surface of the wires. The coating of fabrics with polytrifiuorochloroethylene renders the fabrics fire proof and shrink resistant and increases the strength of the fabrics.

Heretofore the normally solid polymer has been applied to the surface by melting the polymer and applying it to the surface, such as by extrusion, or by dissolvingpthe solid polymer in a suitable solvent, coating the surface with the solvent and' subsequently evaporating the solvent. Applying the solid polymer by extrusion to the surfaces has certain obvious disadvantages. One of these disadvantages is the fact that relatively high temperatures must be'employed and at such high temperatures there is a tendency for the polymer to decompose. The decomposition of the polymer not only affects its chemical and physical characteristics, but also the products of decomposition may attack the surface which is being coated.

It is also difficult to obtain thin films upon the surface when applying the polymer by extrusion, the use of thin films being highly desirable in coating wires used, for example, as armatures of motors. The solution method of application also has certain disadvantages. The substantial insolubility of the polymer in most solvents and its high viscosity with low solids content in other solvents makes this method somewhat impractical. Those solvents which have been found useful for dissolving plastic polytrifluorochloroethylene are relatively expensive which necessitates their recovery afterevaporation. The solvents may also be corrosive to the surface being coated at the condition of application. The relatively high viscosity of solutions of plastic polytrifluorochloroethylene also makes their application difficult and the solutions must usually be applied at substantially elevated temperatures.

It is the object of this invention to form stable dispersions or suspensions of normally solid polymers of trifluorochloroethylene.

Another object of this inventionis to provide a method for applying plastic polymers of trifluorochloroethylene of modified characteristics to surfaces.

Still another object of this invention is to provide a method and material fordispersing and plasticizing the plastic polymer of trifiuorochloroethylene in such a form that the dispersion may be applied to surfaces with a minimum of application difficulties.

Another object of this invention is to provide a dispersion of plastic polymer of trifluorochloroethylene .and a plasticizer in high concentrations and low viscosities in a liquid medium.

Various other objects and advantages of the present invention will become apparent to those skilled in the art.

Accordingly, finely-divided plastic polymer of trifluorochloroethylene is directly dispersed or suspended in a liquid medium. Suitable dispersants are the aliphatic and aromatic esters, the ether alcohols, and the ketones, having at least 3 carbon atoms per molecule and having a surface tension of at least about 23 dynes/cm. at 20 C. Suitable ketones, useful as dispersants, comprise methyl isobutyl ketone, methyl ethyl ketone, di-isobutyl ketone, isophorone and cyclohexanone. Suitable ether alcohols, useful as dispersants, comprise the monoether alcohols such as methoxy ethanol, ethoxy ethanol, butoxy ethanol and the di-e'ther alcohols such as ethoxy ethoxy ethanol. Suitable esters, useful as dispersants, comprise methyl acetate, ethyl acetate, butyl acetate, ethyl propionate, amyl acetate and ethyl benzoate. The concentration of plastic polymer in the liquid medium rangesbetween about and about 30 percent by weight usually in a particle size of about 0.1 to about 10 microns. In addition to the dispersant, the liquid medium preferably includes a diluent. The preferred diluent is an aromatic hydrocarbon, such as xylene, toluene, or benzene. Hydrocarbon fractions containing a relatively large amount of aromatic hydrocarbons are also suitable as the preferred diluent, such fractions being naphthas and petroleum distillates. Although the aromatic compounds are much preferred as diluents to be employed together with the: dispersant as the liquid suspending medium, certain other compounds may be employed as diluents. These other compounds include the aliphatic alcohols having two or more carbon atoms per molecule, unsubstituted others such as dibutyl ether, and relatively high boiling hydrocarbon fractions. Mixtures of alcohol and water in a volume ratio of about 1:1 to about 1:5 have been found suitable as diluents for the dispersant. The weight ratio of dispersant to diluent is in the range of about 1:2 to about 1:25, preferably in the range of about 1:2 to 1:10. The preferred dispersing medium consists essentially of di-isobutyl ketone and xylene in a weight ratio of about 1:4.

vA dispersion of the plastic in an aromatic hydrocarbon,

such as xylene, may be made without the use of a dispersant. The aromatic hydrocarbon has a tendency to swell the plastic much like the dispersants. That amount of the aromatic hydrocarbon which swells the plastic may be regarded as the dispersant and the excess as the diluent. Dispersions made with an aromatic hydrocarbon alone, however, are generally not as good as those made with the above dispersants.

According to this invention it has been found desirable in making up the dispersion or suspension of the plastic to include a suitable plasticizer for the plastic trifluorochloroethylene polymer. In this manner the ultimate film obtained is more resilient and pliant, with less tendency for the film to tear or scratch. The use of a plasticizer also prevents crystallization of the plastic film with age. Such plasticizers comprise normally liquid and waxy polymers of trifiuorochloroethylene. The liquid and wax polymers of trifiuorochloroethylene are produced in a similar manner as described with regard to the production of normally solid polymers of trifiuorochloroethylene. In general, the wax and liquid polymers are obtained at higher temperatures and with greater concentrations of promoter, usually with a chain transfer solvent, than employed in the manufacture of plastic polymers. Other plasticizers which may be incorporated with the dispersing medium comprise dioctyl phthalate and tricresyl phosphate. The plasticizers are incorporated in the dispersing medium in substantially the same amount as the polymer, usually in the range of about 10 to 25 weight percent of the dispersing medium.

According to this invention, films of 0.1 to 5 mils in thickness of normally solid polymer of trifluorochloroethylene may be applied to metal surfaces or the like. The normally solid polymer of trifluorochloroethylene is ground in a mill to a suflicient extent that the powdered polymer passes an mesh screen. Thereafter, the powdered polymer is mixed with the dispersing medium of the composition as previously described. Generally, the solid polymer is incorporated in the dispersing medium initially in an amount not over 17 weight percent. The mixture of solid polymer and liquid dispersing medium is then introduced into a ball mill or pebble mill for further grinding. The grinding is com tinued for a period of at least twenty-four hours and thereafter an increased amount of solid polymer is introduced into the mixture during ball milling to bring the concentration of solid polymer to about 20 to 30 weight percent. The ball milling is continued for another period of at least twenty-four hours. Generally, the ball milling operation is effected over a period of about four to about eight days. Any method of grinding and pulverizing the powdered polymer may be employed without departing from the scope of this invention. Roller mills, colloid mills, gear pumps, and other conventional devices may be employed. After a suificient length of ball milling, the mixture contains finely dispersed solid polymer of about 1 micron in diameter which does not settle upon prolonged standing and has a viscosity of about to centipoises at room temperature.

After the dispersion of plastic of the desired concentration has been made, preferably the plasticizer is then added to the dispersion to impart the modified characteristics to the dispersion. The plasticizer is substantially all dissolved in the dispersing medium. It is important to dissolve the plasticizer in the dispersing medium after the plastic has been dispersed since the presence of the plasticizer during milling makes the pulverization of the plastic into small particles difiicult. Although the above procedure for incorporating the plasticizer in the dispersion is preferred, the plasticizer may be added prior to milling, as disclosed in the examples, without departing from the scope of this invention.

Articles may be coated by dipping the liquid into the above mixture and air drying. A coating of not more than: aboutt one mil in: thickness can be obtained by a single dip. Usually; two; 'three or'i-mn're dipspwith air drlyingrbetween' dips; are required" to"obtain=' the desired fil'rn "thickness upon the surface of-the' article. After the 'last'dip' the surface "containingIthe 'deposited solid plasticized polyiner thereon is heated to. a temperature of'abou't 200 C. or'higher, dependingwonthe: amount and type of plasticizer employed, for from seconds to ZS -minutes tocaus'e fusion and sintering of the solid powdered particles "ofpo'lymer; Shorter periods of time within the above range are permissible with higher temperatures of fusion. The lower temperatures of fusion are preferred ---since the tendency of the polymer to decompose. and attack l metal surfaces: is .minimized. If insufficient film-thickness isobtained-after about four applications followed by fusion, the entire procedure ma be repeated until the desired film thickness is obtained Other methods Of ap IicatiOninclude spraying and painting. On rigid metal surfaces, it may be-desirable to lower the temperature following. fusion at. a slow. rate, givingbetter adhesion. On the other hand, when flex'ibilityand toughness are required; a. quick quench of thefused film will-be necessary to obtain an essentially amorphous polymer.

Fillers may-be added to-t'he. completed dispersion with gentle. stirring or by addition prior to the. grindingoperation' in the pebble mill. Examples of stable fillers are calcium silicate, calcium carbonate, carbon black. titanium dioxide, etc., with particle dimensions of approximately 015 micron in diameter. Pigments such as the phthalocyanines andchrome green can also be incorporated in the polytrifiuorochloroethylene dispersions.

The following examples are ofiered as abetter understanding of the invention and should not beconstrued as unnecessarily limiting thereto.

EXAMPLE I About grams of 314 N. S. Tfpolytrifluoro'chloroethylene plastic (through '80. meshscreen) was added with stirring to a liquid dispersing medium containing 71 grams of di-isobutyl ketoneand 15.6 grams of. xylene. Thesuspensionwaspoured'into a one quart pebblevmill containing450 'cc. offlint'pebbles and rotated at approxi mate1'y75 R. P. 'M. for. 85 hours. This dispersion, containing' 16.5 percent plastic, flowed readily and gave complete visual coverage of a metal or glass surface whether applied byspraying, dipping, or drawing on the object'co'ated The dispersion dries to a white powdery material which formsa' continuous film when heated to a"tem'perature of'390 C. to4l5 C. forififteen seconds. After two or three applications, a continuous coating providing excellent'cliemical resistance to glass and good electrical insulation tdrnetal is obtained.

[EX MPLE 11 f About 42"gramsof= 3 14"N. S. T. polytrifluorochloro- 'ne"plastic- (through '80 mesh screen)"wasadded itlu'id dispersing mediumcontaining' 30 gr'ams of I 'choloro't'rifluoroethylene polymer, 41 "grams of di isobutyl 'ketone and -1'56 grams "of xylene. This suspension was added to a quart size pebble mill containing 450cc. offiint pebbles'and' rotated at 'approxirnately 1*10 RS 'P; M. for about' sixty-nine hours. The dispersion exhibited the properties as described in E'xa'r'i iplel' with the exceptionthata fusion temperature of 380 "-C. to 400 C; is used to produce a continuous III About 42 grams of 314 N. S. T. polytrifiuorochloroethylene plastic (through 80 mesh screen) was added with stirring. to a liquid" dispersion medium consisting of 30 grams of lliquid chlorotrifiuoroethylene polymer, 41 i of di iso'butyl ketone. and 156 grams of xylene. us'pensibnwafsadded to a 'quart' size ball-mill con tai ng '0"c'c; of"stainles's"'ste'e1 balls and rotated at approximately'@ R. P: mrer issss hours. To jthi's exeellentdi'spersion was ad'd'ed" 6 =grams df31'4N. S. T. polytrifluorochloroethylene plastic and the material milled at the sa'me rate for an additional 63.5 hours. The dispersion d'ries to a white powdery material which forms a continuous film when heated to 380 C. to 400 -C. for fifteen seconds. After two or three applications, a continuous "coating providin'g excellent chemical resistance toglass and goo'd electrical insulation to metal is obtaine'd.

EXAMPLE IV 45 grams of '314 'N.,S. T. polytrifluorochloroethylene plastic v(throughmesh screen) was covered with grams of di-isobutyl ketone and allowed to stand for one week. The ketone was filtered from the plastic which contained approximately 2.5 percent of dissolved ketone. The 47.5 grams of ketone-containing plastic was added to a liquid dispersing medium containing 68.5 grams of di isobutyl ketone, and 156 grams of xylene. The suspension was placed in a; quart pebble mill containing 450'cc. of' flint pebbles and rotated for 48 hours. The dispersion dries to a white powdery material. which forms a' 'continuous film when heated to 380 C. t6 400 C. for fifteen seconds. After two or three applications, a continuous coating providing. excellent chemical resistance toglass and good electrical insulation to metal is obtained. I

' EXAMPLELV A dispersion similar to that of Example I was employed in this example to coat copper wire. In order to obtain complete coverage on' the copper wire; it' was necessary to dip the'wire three times, 7 allowing the particle film to beheated to C. for fifteen seconds be tween successive dips. After the third dip, the wire was inserted into a furnace at 390 C. for short periods of 20-30 seconds until the particles appeared to be fused without evidence of decomposition. This cycle of multiple' dipping and heating followed by fusion after every third dip was repeated three times and the Wire was elec trically insulated. At this stage,-a diameter increase of 26 mils was measured which represents a film thickness of 1.3 mils assumingthe wire was coated uniformly. The film showed no evidence of cracking after bending the wire sharply several times. It seems likely that better coverage of the copper wire with the resulting decrease in-the'number ofdipping operations required toobtaina filmthicknessof l-Z mils can be accomplished by increas ing the viscosity of the dispersion.

EXAMPLE VI About 45 grams of 240 N. S. T. polytrifluorochloroethylene plastic (through 80 mesh screen) was added with stirring to a liquid dispersing medium containing 71 grams of di-isobutyl ketone and 156 grams of xylene. The suspension was poured into a one quart pebblemill contaniing 450 cc. of flint pebbles and rotated at approximately 75 R. P. M. for 85 hours. This dispersion, containing 16.5 percent plastic, flowed readily andgave complete visual coverage of a metal or glass surface whether applied by spraying, dipping or drawing on the object coated. The dispersion dries to a white powdery material which forms a continuous film when heated to 375 C. to 390 C. for fifteen seconds. 1 The above proceduregave a continuous film from 0.1 mil to about 0.3 mil in thickness.

EXAMPLE VII pebbles half filling the mill; The liquid just covered the -hours. The free-flowing colloidally dispersed plastic gave good coverage tometal and glass surfaceswhen the latter were dipped into the dispersion. After air-drying, the plastic particles were fused to a continuous film by heating to 390-415 C. for from fifteen seconds to one minute.

Addition of sufficient plastic in the above example to make the total concentration 23 percent and 48 hours of pebble milling produced a dispersion which exhibited thixotropic properties. Due to the buttery gel-like nature of the product, it is diflicult to apply to metal and glass surfaces.

EXAMPLE VIII About 260 grams of polytrifluorochloroethylene wax (M. P. 98 C.), 36 grams of 240 N. S. T. polytrifluorochloroethylene plastic, and 140 grams of xylene were placed in a quart size pebble mill and milled for 96 hours. The dispersion contained 67.9 percent total solids, and the ratio of plastic to wax was 12.88. Paper suitable for bottle cap liners was dipped into the dispersion, air-dried, and heated to 200 C. for a short time. A continuous coatingof wax plastic approximately 1 mil thick was formed on the surface of the paper and imparted watervapor imperrneability, gas impermeability, flame resistance, resistance to chemicals, etc., to the paper.

EXAMPLE IX About 150 grams of polytrifluorochloroethylene wax (M. P. 98 C.), 50 grams of 240 N. S. T. polytrifluorochloroethylene plastic, and 238 grams of xylene were placed'in a quart size pebble mill and milled for 96 hours. The resulting dispersion contained 45.6 percent total solids and a plastic to wax ratio of 25:75. The dispersion was sprayed onto tin coated iron and fused at 200 C. for five minutes. A continuous 2 mil protective coating was formed.

7 EXAMPLE X About 60 grams of polytrifluorochloroethylene wax (M. P. 70 C.), 60 grams of 300 N. S. T. polytrifluorochloroethylene plastic, and 275 grams of xylene were placed in a quart size pebble mill and milled for 96 hours. The resulting dispersion contained 30 percent total solids and a plastic to wax ratioof 1:1. The dispersion was brushed onto aluminum surfaces, air-dried, and fused at 235 C. for five minutes. A hard well-adhering protective film was formed on the aluminum.

In the above Examples VIII, IX and X substantially all of the wax was dissolved in the xylene. The percent solidsfin the dispersion, therefore, represents both undis'solved plastic and dissolved wax.

EXAMPLE XI 46.2 grams of 300 N. S. T. polytrifluorochloroethylene plastic (screen analysis indicated 66 percent through 80 mesh) was added with stirring to a thinner consisting of 41grams of butyl acetate and 186 grams of xylene. This suspension was charged to a quart size ball-mill jar containing approximately 450 mils of flint pebbles and rotated for 139 hours. To this excellent dispersion was added 10.2 grams of 300 N. S. T. plastic and milling continued for 96 additional hours. The resultant dispersion (20-percent plastic) was too viscous for adequatefilm deposition by dipping and was diluted with stirring by the addition of 12.8 gram of butyl acetate and 57.9 grams of xylene. The final dispersion (16 percent KEL-F) deposited an even film of KELF particles which fused to a continuous coat at 380 C. to 400 C.

EXAMPLE XII 46.2 grams of 300 N. S. T. polytrifluorochloroethylene plastic (screen analysis indicated percent through 80 mesh)lwas added with stirringito a thinner consisting of 41 grams of methyl isobutylketone and 186. grams of xylene. This suspension was charged to a quart size pebble-mill jar containing approximately 450 mils of flint pebbles and rotated forf139 hours. To this dispersion was added.10.5 grams of the 300 N. S. T. plastic and milling continued for 47 hours. .The resultant dispersion (20 percent plastic) was excellent. The final dispersion deposited an even' film of plastic polytrifluorochloroethylene particles which fused at 380 C. to 400 C.

EXAMPLE, XIII About 46 grams of 300 N. S. T. polytrifluorochloroethylene plastic (screen analysis indicated 66 percent through 80 mesh) was added with stirring to a thinner consisting of 41 grams of '2,ethoxy-ethanol,1 and 186 grams of xylene. This suspension was charged to a quart size pebble-mill jar containing approximately 450 mils of flint pebbles and rotated for 139 hours. To this dispersion was added 10.5grams of the 300 N. S. T. plastic and milling continued for 47 hours. The resultant dispersion (20 percent plastic) was excellent but was slightly more viscous than desirable, depositing a thick film upon dipping. 4.5 grams of xylene and 1 gramof 2,-ethoxyethanol,1 were added, and milling continued for 28 hours. The final dispersion (19.6 percent plastic) deposited an even film of plastic polytrifluorochloroethylene particles which fused at 380 C. to 400 C.

Copper wire was coated with thin films of polytrifiuorochloroethylene plastic by means of dispersions of suitable viscosities and a Hytron unit which is used in the wire coating field for preliminary evaluation of wire insulating materials prior totests in commercial wire coating units. The Hytron unit consists of a baking oven, approximately 21 inches in length, which can be heated to a maximum temperature of 1000. C., of two applicators which are located within about 8 inches of either end of the oven and which canbe used separately or in combination, and of conventional apparatus for regulating the speed of the wire through the oven and for guiding the wire for multiple coating. Recycling the wire back and forth through the applicators and the oven is to build up the wall thickness.

The wire, A. W. G. No. 28, was coated at various rates from 2 ft./min. at 400 C. to 20 ft./min. at 720 C. The temperatures recorded were the air temperatures of the oven. The time in the oven varied from approximately 53 seconds at the low rate to 5 seconds at the high rate.

By multiple coating it is possible to build up coatings 5 mils (0.005 inch) ormore in thickness; by increasing the viscosity of the dispersion, e., by increasing the plastic concentration, fewer applications are required. For example, wire was coated with a film 1 mil thick by passing the wire 8 times through a single applicator containing a 20 percent plastic dispersion, with and without a plasticizer. When the concentration of the dispersion was adjusted-to 30 percent plastic, only 4 passes through a single applicator were required. Both of these coatings used a wire rate of 14 ft./min., oven temperature of 600 C., and the Wire remained in the oven 7.6 seconds per pass.

The thin polytrifluorochloroethylene plastic coatings possessed good mechanical and 'electricatlproperties and good chemical resistance.

Paper, fabric, and ceramic sheets coated with trifluorochloroethylene polymers are used as ,jackets for the insulation of wire and cable. The fabrics or papers are applied in the form of tapes, sheets, or braids. For high temperature resistance insulators the straight polytrifluorochloroethylene plastic dispersion is used to coat the wrapping. Polytrifluorochloroethylene wax-plastic dispersions may be used in applications where high temperature resistance is not needed. A final polytrifluorochloroethylene coat may be placed over the wrapped wire, if desirable.

The dispersions may be used tocoat individual or mullow moisture'absorption, and good chemical'resistance of the poly trifluorochloroethylene coating. A specific example is coating of copper magnet wire for motor armatures and generators.

The dispersions maybe used as saturants for the treatment of asbestos braids (plus fusion treatment) employed on a numberof small power cables, switchboard, and stove wires.

Dispersions of polytrifluorochloroethylenes are particularly useful in thin-walled electrical insulation, coating of electrical assemblies such as condensers, resistors, and the tortion point. 1

Protection of metal against the various service condinons re whichit may be exposed is solved in numerous cas's'"by"coating' the exposed surface with polytrifiuorochloroethyle'he applied from dispersion. A specific exampleis' the coating of large gate valves made of steel. Thevalves 'are to be used in a highly corrosive acid solution" at 80-90" C. The surface of the metal to be coated is "pretreated by solvent dip followed by mild pickling in order to obtain optimum" adhesion of the polytrifluorochloroethylene film. A 20 percent plastic dispersion is pas'sedover the surface to be coated and the coated valve drained, air-dried and fused for two minutes at 390 C. This operation is repeated in order to makecer'tain that no exposed surfaces,remaina The resulting continuous film had a thickness of'liS mils and successfully protected the gate valve near corrosion. Another example is the coating of the inside of an aluminum tank with polytrifluorochloroethylene wax-plastic dispersion so that it will .withstand the action of white-fuming and dilute nitric acid and vapors at temperatures up to 80 C. The tank is partially filled with the polytrifluorochloroethylene waxplastic dispersion, rotated to completely wet the internal surface, drained, dried by passing a warm inert gas into the tank, and fused at 200 C. for ten minutes. This operation is repeated two more times and a continuous nonporous film 1 mil thick built up which meets the desired specification.

The above wax-plastic dispersion is especially suited for the coating of cans. A fusion temperature of 200 C. for ten minutes is suitable in the can coating industry and this inert film formed does not impart odor, color, or taste to the can ingredients.

The dispersion is deposited on the surface of the metal to be used in making cans by means of conventional roller coating techniques.

The present invention includes within its scope polymers of trifluorochloroethylene which include a minor amount of other monomers, such as vinyl chloride, tetrafiuoroethylene, perfiuoropropene and acrylonitriles. The use of these other monomers is limited to less than about 15 percent of the polymer. In some instances it is desirable to use small quantities of other monomers in combination with the principal monomer trifluorochloroethylene in order to impart modified characteristics to the resulting polymer.

We claim:

1. A dispersion which comprises finely-divided particles of the plastic homopolymer of trifluorochloroethylene and an added waxy polymer of trifluorochloroethylene as a plasticizer dispersed in a liquid dispersing medium comprising di-isobutly ketone and xylene.

2. The method for preparing a dispersion of the plastic homopolymer of trifluorochloroethylene which comprises admixing the plastic homopolymer of trifluorochloroethylene and an added polymer of trifluorochloroethylene having a molecular weight no higher than that of the like, requiring low moisture absorption and high heat diswaxy polymer as a plasticizer with a ketone having at least three carbon atoms permolecule as a dispersant and xylene as a diluent and milling the plastic polymer while in admixture with the ketone and xylene for at least 24 hours to form a dispersion.

3. The method for preparing a dispersion of a plastic polymer of trifluorochloroethylene containing less than 15 percent of an ethylenically unsaturated compound other than trifluorochloroethylene as a comonomer therein which 7 comprises admixing said plastic polymer of trifluorochloroethylene and an added polymer of trifluorochloroethylene having a molecular weight no higher than that of the waxy polymer as a plasticizer with an organic dispersing medium comprising at least one compound selected from the group consisting of ether alcohols and ketones and milling the plastic polymer while in admixture with said organic dispersing medium to form a dispersion.

4. A dispersion which comprises a plastic homopolymer of trifluorochloroethylene and an added waxy poly-' mer of trifluorochloroethylene as the plasticizer dispersed in a liquid organic dispersing medium comprising at least one compound selected from the group consisting of ether alcohols and ketones. 1

5. A liquid suspension comprising (1) a dispersed phase consisting essentially of finely divided solid, high molecular weight polychlorotrifluoroethylene as the sole polymeric ingredient in the solid state and (2) a dispersion medium for (1) comprising (a) a low molecular weight liquid polymer of chlorotrifluoroethylene and (b) an aliphatic ketone having at least three carbon atoms per molecule.

6. A liquid suspension comprising'fl) a dispersed phase consisting essentially of finely divided solid, high molecular weight polychlorotrifluoroethylene as the sole polymeric ingredient in the solid state and (2) a dispersion medium for (1) comprising (a) a low molecular weight liquid polymer of chlorotrifluoroethylene and (b) a ketone.

7. A dispersion which comprises a plastic polymer coni taining more than 85 percent of the monomer trifluorochloroethylene and containing less than about 15 percent of an ethylenically unsaturated compound other than trifluorochloroethylene as a comonomer therein, an added waxy polymer of trifluorochloroethylene as a plasticizer,

, dispersed in a liquid organic dispersing medium comprising as a dispersant at least one compound selected from the group consisting of the ether alcohols and the ketones.

8. A dispersion which comprises a plastic polymer of trifluorochloroethylene containing less than about 15 percent of an ethylenically unsaturated compound other than trifluorochloroethylene as a comonomer therein and a plasticizer selected from the group consisting of liquid and waxy polymers of trifluorochloroethylene, dioctyl phthalate and tricresyl phosphate dispersed in a liquid medium comprising as a dispersant at least one compound selected from the group consisting of ether alcohols and ketones.

9. A dispersion which comprises a plastic polymer of trifluorochloroethylene containing less than about 15 percent of an ethylenically unsaturated compound other than trifluorochloroethylene as a comonomer therein and an added polymer of trifluorochloroethylene having a molecular Weight no higher than that of the waxy polymer as a plasticizer dispersed in a liquid medium comprising as a dispersant at least one compound selected from the group consisting of ether alcohols and ketones.

10. A dispersion which comprises a plastic polymer of trifluorochloroethylene containing less than about 15 percent of an ethylenically unsaturated compound other than trifluorochloroethylene as a comonomer therein and an added polymer of trifluorochloroethylene having a molecular weight no higher than that of the waxy polymer as a plasticizer dispersed in a liquid organic dispersing medium comprising at least one compound selected from the group consisting of ether alcohols and ketones, the concentration of plastic in the dispersion being between about and about 30 percent by weight and the concentration of plasticizer in the dispersion being between about 10 and about 25 percent by weight.

11. A dispersion which comprises a plastic polymer of trifluorochloroethylene containing less than about percent of an ethylenically unsaturated compound other than trifiuorochloroethylene as a comonomer therein and an added polymer of trifiuorochloroethylene having a molecular weight no higher than that of the waxy polymer as a plasticizer dispersed in a liquid medium comprising an organic dispersant and an organic diluent, said dispersant comprising at least one compound selected from the group consisting of ether alcohols and ketones, the concentration of plasticizer in the dispersion being between about 10 and about percent by weight, the weight ratio of dispersant to diluent being between about 1 to 2 and about 1 to 25 and the viscosity of the dispersion being less than about 130 centipoises.

12. A dispersion which comprises a plastic polymer of trifiuorochloroethylene containing less than about 15 percent of an ethylenically unsaturated compound other than trifiuorochloroethylene as a comonomer therein and an added waxy polymer of trifluorochloroethylene as a plasticizer dispersed in a liquid organic dispersing medium comprising at least one compound selected from the group consisting of ether alcohols and ketones.

13. A dispersion which comprises finely divided particles of the plastic polymer of trifiuorochloroethylene containing less than about 15 percent of an ethylenically unsaturated compound other than trifluorochloroethylene as a comonomer therein and an added waxy polymer of trifluorochloroethylene as a plasticizer dispersed in diisobutyl ketone.

14. A dispersion which comprises finely divided particles of the plastic polymer of trifluorochloroethylene containing less than about 15 percent of an ethylenically unsaturated compound other than trifiuorochloroethylene as a comonomerthereinandan added polymer of trifluorochloroethylene having a molecular weight. no higherthan that of the waxy polymer as a plasticizer dispersed.

in methyl. isobutyl ketone.

than that of the waxy polymer as a plasticizer dispersed in xylene.

-16. A dispersion which comprises finely divided par-- ticles of the plastic polymer of trifluorochloroethylene containing less than about 15 percent ofan ethylenically unsaturated compound other than trifluorochloroethylene as a comonomer therein and an added polymer of trifiuorochloroethylene having a molecular weight no higher than that of the waxy polymer as a plasticizer dispersed in methoxy ethanol.

17. The method of preparing a dispersion of the plastic polymer of trifluorochloroethylene containing less than about 15 percent of an ethylenically unsaturated compound other than trifiuorochloroethylene as acomonomer. therein and a plasticizer selected from the group consisting of liquid and waxy polymers of trifluorochlorQ- ethylene, dioctyl phthalate and tricresyl phosphate with an organic dispersing medium comprising'at least one 1 compound selected from the group consisting of ether alcohols and ketones and pulverizing the plastic polymer while in admixture with the dispersing medium for at least twenty-four hours to form a dispersion.

References Cited in the file of this patent UNITED STATES PATENTS 2,484,483 Berry Oct; 11', 1949 2,510,078 Compton et al June 6, 1950 2,581,454 Sprung Jan. 8, 1952 

1. A DISPERSION WHICH COMPRISES FINELY-DIVIDED PARTICLES OF THE PLASTIC HOMOPOLYMER OF TRIFLUOROCHLOROETHYLENE AND AN ADDED WAXY POLYMER OF TRIFLUOROCHLOROETHYLENE AS APLASTIZER DISPERSED IN A LIQUID DISPERSING MEDIUM COMPRISING DI-ISOBUTLY KETONE AND XYLENE. 